This invention relates to the field of undervoltage release mechanisms for circuit breakers.
In addition to mechanism for opening the contacts of a circuit breaker automatically on occurence of short circuits or excessive current conditions, it is often desirable to provide means to open the contacts automatically when an undervoltage condition occurs. Such means typically includes a separate coil and armature to actuate the tripping mechanism on occurrence of a low voltage condition. Ordinarily the armature is attracted to the coil when energized at full voltage, the armature being biased at a selected tension to move away from the coil when voltage supplied to the coil and the circuit breaker drops below a selected amplitude.
Previously known circuit breakers equipped with low voltage mechanism of this type are susceptible to damage if an attempt is made to close the breaker while it is energized with inadequate voltage, or not energized at all. Under such conditions, the low voltage mechanism may allow the breaker to trip during the closing stroke which can damage the breaker.